Digital microfluidics is an alternative paradigm for lab-on-a-chip systems based upon micromanipulation of discrete droplets. Microfluidic processing is performed on unit-sized packets of fluid which are transported, stored, mixed, reacted, or analyzed in a discrete manner using a standard set of basic instructions. In analogy to digital microelectronics, these basic instructions can be combined and reused within heirarchical design structures so that complex procedures (e.g. chemical synthesis or biological assays) can be built up step-by-step. And in contrast to continuous-flow microfluidics, digital microfluidics works much the same way as traditional bench-top protocols, only with much smaller volumes and much higher automation. Thus a wide range of established chemistries and protocols can be seamlessly transferred to a nanoliter droplet format.
Research in Dr. Richard Fair's laboratory at Duke University has focused on the use of electrowetting arrays to demonstrate the digital microfluidic concept. Electrowetting is essentially the phenomenon whereby an electric field can modify the wetting behavior of a droplet in contact with an insulated electrode. If an electric field is applied non-uniformly then a surface energy gradient is created which can be used to manipulate a droplet sandwiched between two plates. Electrowetting arrays allow large numbers of droplets to be independently manipulated under direct electrical control without the use of pumps, valves or even fixed channels.
K. Hu, B.-N. Hsu, A. Madison, K. Chakrabarty and R. Fair "Fault Detection, Real-Time Error Recovery, and Experimental Demonstration for Digital Microfluidic Biochips" Monitoring Active Filters under Automotive Aging Scenarios with Embedded Instrument, pp. 559-564, 2013 PDF
M. W. Royal, N. M. Jokerst and R. B. Fair "Droplet-Based Sensing: Optical Microresonator Sensors Embedded in Digital Electrowetting Microfluidics Systems" IEEE Sensors Journal, vol. 13, no. 12, December 2013, pp. 4733-4742 PDF
B.-N. Hsu, A. C. Madison and R. B. Fair "Accelerate Sepsis Diagnosis by Seamless Integration of DNA Purification and qPCR,"Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences (microTAS '12), Okinawa, Japan, October 28-November 1, 2012, pp. 830-832. PDF, Poster
M. W. Royal, N. M. Jokerst, and R. B. Fair "Integrated Sample Preparation and Sensing: Polymer Microresonator Sensors Embedded in Digital Electrowetting Microfluidic Systems," IEEE Photonics, vol. 4, pp. 2126-2135, 2012. DOI
M. W. Royal, R. B. Fair, and N. M. Jokerst "Integrated Sample Preparation and Sensing: Microresonator Optical Sensors Embedded in Digital Electrowetting Microfluidics Systems," Proceedings of the 10th IEEE Sensors Conference, Limerick, Ireland, October 28-31, 2011, pp. 2050-2053. DOI
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Chip mixes droplets faster, MIT Technology Review, October 2003.
Chip Juggles Droplets, Technology Research News, Sep. 4-11, 2002.
Digital Microfluidics, Slashdot, August 3, 2002.
Laboratory on a Chip, Popular Mechanics, March 2002.
Lab-on-a-Chip Technology May Present New ESD Challenges, Electrostatic Discharge Journal, March 2002.
Making Materials Fit the Future, R&D Magazine, December 2001.
Email: rfair AT ee.duke.edu
Department of Electrical and Computer Engineering
Durham, NC 27708